Wadhams on seaice, again

and so on. Its all sourced to “an email to the Guardian” which unfortunately they don’t reproduce. Now is the time to mention the Arctic Methane Emergency Group of which Wadhams is a member, to his discredit.

There is some strange stuff in the article, such as [Wadhams] predicted the imminent break-up of sea ice in summer months in 2007 which I don’t think is true – certainly, no-one predicted that 2007 would be unusually low, as far as I know [*]. It does quote him as saying I have been predicting [the collapse of sea ice in summer months] for many years which isn’t too impressive – it rather sounds like he has been predicting it, but it hasn’t happened, but he’s hoping (so to speak) that now he’s right: This collapse, I predicted would occur in 2015-16 at which time the summer Arctic (August to September) would become ice-free. The final collapse towards that state is now happening and will probably be complete by those dates. But I’m not sure where those predictions were may. And we don’t know quite what he means by “ice-free”.

I’ll be doing the round-up of the bets at the end of September, if you were wondering.

,“If his calculations are correct then that means that over recent decades the melting of the Arctic ice cap has put as much heat into the system as all the CO2 we have generated in that time”

I’d expect better from the BBC but perhaps they don’t realise it is crap

[I don’t think its obvious nonsense. It might even be true, or possibly true-with-certain-assumptions. Picking numbers from nowhere, I think 0.5% of insolation change is substantial. So if Arctic sea ice goes from 2% to 1% of earths area, and changes from 80% to 30% albedo, then hey presto you have 0.5% insolation forcing, sort of. Ignoring various important things. So, you’d need to see the details of his calculation -W]

I wish I could get a story in the Guardian just from writing an email….

[Perhaps you’re saying the wrong things ;-? -W]

But some numbers are in order (JJA, 60-90N, taken from the GCM – so ballpark correct, if not exact):
Incoming SW: ~425 W/m2
Planetary Albedo: ~40%
Downward SW at Surface: ~230 W/m2
Net Surface Albedo: ~35%

Impact of loss of summer ice for a month(?) is a shift of ground albedo from 0.50 (summer ice is already darker than snow-covered ice) to 0.08 (ocean – including zenith angle effects), so over the season, an average change of 0.42 for a third of the time, for 65% of the surface… i.e. 0.09. This is a surface flux perturbation of ~20 W/m2. At the TOA it is smaller because of compensating cloud effects – perhaps by half, so 10 W/m2. At the surface you’d have to include LW impacts as well so it would be less also.

And this is for 3 months for 14% of the globe. Giving a net radiative effect of 0.35 W/m2.

Last 20 years of CO2 increase was about 42ppm. Which is about 0.6 W/m2. So he is probably out by about a factor of two.

[OK, so my off-the-top-of-my-head estimate wasn’t so bad. The question is though, has Wadhams done this kind of back-of-envelope calc, or something more precise? Given his background, I’d suspect BoE. But its irritating to have to guess – he could just say -W]

But that isn’t even the biggest problem which is that this is a feedback and not a forcing. Since the feedback was presumably present in any observationally constrained estimate of the climate sensitivity, this effect can’t possibly be used to argue for an increased sensitivity over expectations.

[Yes, but he isn’t claiming this as a reason for increased sensitivity. I’m not quite sure just what he is using it for – really, its just an illustration of how big a radiative perturbation it is, compared to CO2, which is probably quite a useful idea, as AG says -W]

The ocean heat argument is also backwards. OHC is increasing because of the radiative imbalance and conservation of energy. Since the imbalance is driven by the increase in GHGs, compensated for by the response of the surface temperature, anything that increases surface temperature is actually serving to reduce the imbalance (and hence the OHC change), not increase it. To only look at the SW feedback in this context is very incomplete.

Extent increasing 300k Km^2 per day might get close to saving your bets with Neven and me. (Average rate of increase for last 11 years over this period is about 37k so you only need about 8 times faster than typical 😉 )

As far as I know, the value of 15% as the threshold for ice extent comes from sea ice modeling. It shows up in Hibler’s 1979 ice dynamics model (possibly earlier) which is the basis for dynamics models used in GCMs today. NSIDC’s sea ice index looks at the 15% contour of SSM/I ice concentration to determine extent; others also followed. Consistency through the time series is the argument for that.

Operational ice charting (eg US National Ice Center, Canadian Ice Service, others) follow the WMO standards (SIGRID-2 or 3). Ice extent is defined by the 1/10 contour (in practice, very close to the 15% if passive microwave data is being used, but other sources — eg, RadarSAT [synthetic aperture radar], MODIS [visible] — are also used and can “see” ice that the passive µwave cannot),. “Open water” is 0-1/10, but can contain sea ice. “Ice-free” means no ice of any kind.

Prof Wadhams said “the summer Arctic (August to September) would become ice-free”. If we held his feet to the fire, that would be no ice in the Arctic basin from 1 August to 30 Sep. Giving him some wiggle room, I would still insist on “open water” for some period in August/September 2016. The key to his prediction coming true (or not) would be the disappearance of multi-year ice from the Arctic pack.

I could go on about pressure ridges and other things. Brevity is not my strong suit.

I think I’d always looked at the Arctic thing as a feedback, not a forcing, and yes it is already included in estimates of climate sensitivity so one can’t present it in a way that appears to be double-counting, but…
To me the relevant point is that it is happening sooner, and it will accelerate warming — we’ll see those temperatures sooner. In some ways, maybe that’s a good thing if it puts a damper on climate change denial and pushes people and nations to take action. On the other hand, it also means we now have less time to act, and every moment of delay is that much worse.

On the idea that this is a damper… that would be true of surface heating, to some degree, but (a) won’t a lot of the radiation penetrate more deeply into the ocean and (b) because Arctic sea surface temperatures are always so low, isn’t the LWR feedback comparatively small? It’s not like heating the ocean at the equator, after all.

[OK. There is a slight, but for our purposes negligible, difference in the vapour pressure above ice and water, if the two are pure and at the same temperature. If the water is warmer then I agree, there will be more evaporation -W]

My amateur take on the issue.
Summertime ice is a massive heatsink, it melts from above and below. Once you’ve exhausted the heatsink, you still have incoming SW radiation, but now you have additional outgoing LW radiation. Equals additional heat into the atmosphere, hence the atmosphere warms faster, some of the heat will stay in the ocean and get redistributed. Oceans warm faster?
Even if I’ve got the mechanics wrong, without that heatsink you don’t lose that heat.

Here is a second attempt at that post. William, please delete the previous attempt :-(.

[Done -W]

The difference in water vapour pressure at 0C for ice and for water is not very different but ..

During winter the ice is at ~-30C and the water at -2C so there is a considerable difference in vapour pressure.

[Yes, but that’s only temporary. If the air temp is such that the ice would have been at -30 then the water will very soon freeze -W]

They reckon that the heat escaping through leads can be as high as 1 kW per sq metre. In summer the ice is at 0C but once the ice has gone the SST will rise considerably, since it is no longer being cooled by melting ice. Moreover, the solar radiation that was providing latent heat of melting to the ice will now be available to warm the water, and the water vapour produced by the warming water will produce a positive feedback on the SST. Clouds may produce a negative feedback but only if the solar effects produce enough evaporation.
I have long thought that it was the sudden disappearance at the end of the Younger Dryas of the sea ice that stretched from the Arctic to Ireland which caused the rapid climate change that happened then. It was the combination of two positive feedbacks: ice albedo and water vapour, which produced that abrupt warming. In Richard Alley’s book “The Two Mile Time Machine” he say that the temperature in Greenland jumped by 10C in as short a time as 3 years!

Thanks for Wadham’s calculations. I took a quick peek and it looks like the biggest factor he failed to take into account was clouds…as Gavin pointed out he probably slightly overestimated the albedo difference between clear-sky ice vs. clear-sky ocean at 0.5, but cloud coverage is ~85% over that region in the summer and the albedo difference between clouds over ice and cloud over ocean is only around 0.15. So that’s inflated by a factor of about 3 right there, and then Wadham uses the summer estimate without averaging it out over 4 seasons, which probably explains the remainder of the difference. Hudson (2011 JGR) estimates that the ice-free summer scenario would only contribute about 0.3 W/m^2 to the global picture, and that total removal of Arctic sea ice is only about 0.7 W/m^2. http://www.npolar.no/npcms/export/sites/np/en/people/stephen.hudson/Hudson11_AlbedoFeedback.pdf

[Yes, but that’s only temporary. If the air temp is such that the ice would have been at -30 then the water will very soon freeze -W]

But the air temperature is set by the surface temperature. The surface of the ice can quickly radiates its heat away and its temperature drops. This cools the air.

[The temperatures are set by the exchange of energy between the various components, yes. But its not one-way, as you suggest. Nor, I think, is it dominated by radiation -W]

When sea water radiates it heat away, the surface becomes more dense and sinks being replaced by warmer water from beneath. Unlike fresh water, which has a minimum density at 4C, in theory you do not get ice forming on sea water until the whole water column is below its freezing point. In fact cold winds (-10C) formed over land or sea ice can produce ice crystals which float, and form frazil ice. That is why ice forms either from the coast or at the edge of the ice pack. Without an ice pack in the autumn the ice will not be able to reform!

As I understand it “Ice Free” means ice extent of less than a million sq km as measured by NSIDC – ie more than 15% ice.

[Well that’s certainly one definition. Or we could use 0.5; or 2. Why did you pick 1? -W]

There are two things that happened this year that may just be coincidences but may be a result of declining ice. Firstly the major summer storm and secondly the melting over the entire Greenland Ice Sheet.

If we get more frequent summer storms I would expect to see more vertical mixing of the Arctic Ocean. At present there is a cold relatively fresh layer of water about 50 m deep. Below this the water gets progressively more saline and warmer. By contrast other oceans tend to be well mixed to a depth of about 100 m after which the temperature drops progressively. Constant thick ice cover puts a break on wave action. If we get more storms with thin or no ice then I would expect that the Arctic would start to behave more like other oceans. This would bring more heat and salt to the surface which in turn would increase melt and slow down freezing.

[Yeees. But there is a reason the salt is lower down, because its denser -W]

A warmer ocean surface should result in a warmer air column above the arctic. This may result in increased melting of the Greenland Ice Sheet. This years event may be a one off or it may be a portent of things to come.

The Baltic Sea and Hudson Bay both have lower salinities than the Arctic Ocean and that is one reason that they freeze over despite being south of the Arctic Circle. They are also shallow seas so it is easier for the whole water column to fall to freezing point. Finally, they are down wind from ice covered land in winter, so their surfaces can be cooled by the prevailing westerly winds.

Freezing of the Baltic has been increasingly rare in the last decade, one of the signs of what is happening. In any case, what Eli was pointing to is that you don’t need the preconditions others were setting up for a shallow freeze in the Arctic basin.

As W. has pointed out Eli manages to state the obvious “Hudson’s Bay freezes over” but gets the preconditions wrong.

[No, I meant the bit about me losing this year -W]

Hudson Bay does not freeze over until the Arctic is nearly 100% ice covered. The ice spreads from the north coast, so it is reasonable to suggest that if the ice does not form in the Arctic it will not form in Hudson Bay.

You can see how the the ice forms by stepping through Bob Grumbine’s sea ice maps here at my site

You don’t need to go to page 3 of the doc. you cited. On page 1 it says:

[Sure, why bother yourself with trivial details that can only confuse you, when you can read broad sweeping words? -W]

2/ For high Sal waters (S > 25), decreasing temperatures induce convection which continues without the state of maximum density being reached. The temperature decreases till the whole water column is at the freezing temperature. However, freezing of the whole water column can occur only in shallower water.

The NOAA has a nice essay on the various ways sea ice forms. Freezing the whole water column *can* only occur in shallow water. Yet, “It may seem, then, that the whole water column in an ocean has to be cooled to the freezing point before freezing can begin at the surface, but in fact the Arctic Ocean is composed of layers of water with different properties, and at the base of the surface layer there is a big jump in density (known as a pycnocline), so convection only involves the surface layer down to that level (about 100-150 metres).

“In the end, it will just melt away quite suddenly. It might not be as early as 2013 but it will be soon, much earlier than 2040.”

Which probably will be fairly accurate.

And from 2005

“For 40 years I have been measuring sea ice thickness in the Arctic from UK submarines. I first detected substantial thinning in 1990, and since the most recent submarine voyage in 2007 I have been warning that the combination of sea ice retreat and a massive amount of thinning will lead to the disappearance of the summer sea ice by as early as 2015. Despite the fact that this is a simple extrapolation of a clear and measured trend I have been vilified by scientific colleagues for making such a seemingly radical prediction. I am pleased to see these same colleagues now jumping on the bandwagon and supporting my prediction.”

Perhaps he has a point in giving primacy to his measurements rather than the models which we can now see are rather imperfect?

[I’d say that 2005 quote you’ve found it pretty damming, of Wadhams. He’s just extrapolating a trend – which certainly isn’t as clear as he suggests. And the nonsense about vilification just comes across as paranoia. Nor have his colleagues now started agreeing with him -W]

Overall Wadhams just seems to be chiming in on Maslowski’s projection, which is at least model-based with suitable error bars albeit unpublished.

Note that Maslowski also did an extrapolation based on the 2005 loss, coming up with a similar result, IIRC before Wadhams had gone public with anything, but unlike the latter making it very clear that it was just an extrapolation, not a prediction or projection.

I’m all in favor of scientists being able to go public with extrapolations based on their physical intuition, but Wadhams isn’t going about it right.

So Wadhams may be overestimating a bit, but surely is in the right ballpark.

[That was what I said, no? -W]

William said :

He’s just extrapolating a trend – which certainly isn’t as clear as he suggests. And the nonsense about vilification just comes across as paranoia. Nor have his colleagues now started agreeing with him

Was this remark really necessary, William ?
So far, it seems that the trend that Wadhams deduced from ice thickness measurements is more realistic than even CMIP5 trends.

[Its not necessary, of course not. Nor is this one. Is it true – yes, as far as I can tell. Certainly the stuff about vilification is nonsense – in fact, rather self-centered nonsense. Because mostly he hasn’t registered on the radar. As to the trends – well, we disagree on that, we know -W]

Be careful who you talk down upon. Wadhams may be right for the wrong reasons, but that’s still better than being wrong for the right reasons.

William,
As for the amount of abuse that Wadhams incurred for his outspoken opinions in MSM, the blogosphere and even by follow scientists, I wonder why you feel that you can judge him for being “paranoia”.

[I don’t know what you’re talking about. Do you have examples? You’ll need more than one or two, from what you’ve said-W]

As for the projections he makes, let us just look at the science :
When we take 2012 Arctic sea ice minimum (at 3.5 M km^2 or so) I would like to note that Arctic sea ice projections from CMIP3 models are some 3-4 sigma’s too high :

Even when compared to CMIP5 models (in Stroeve et al 2012) extent projections are still about 2 sigma’s too high, and only matched by the models that started off with an unrealistically low extent in the 80’s. (would love to show you the plots, but Stroeve et al is still behind a paywall).http://www.agu.org/pubs/crossref/2012/2012GL052676.shtml

Now in these same plots, I noticed that the 2012 extent matches what the CMIP3 models project for 2060-2070.
At that time, GHG forcing is projected to be about 1.3 W/m^2 higher than present.

So, I ask myself, if the order of the error is only in the range of 1 W/m^2. then could the Arctic simply be a little bit more sensitive than we anticipated ? What if models underestimated climate forcing during the summer by 1.3 W/m^2 ?

And I wonder, could we maybe even identify the issue WHERE GCMs go wrong by some 1.3 W/m^2 ?

William, I ask you as a scientist, what is the probability that the models seriously underestimate snow/ice cover, and that we need consider the very possibility that planet Earth is much more sensitive to an external forcing than even the IPCC models suggest, if the model projections are 2-3 sigma’s off after just 5 years ?

[I’m going to duck out of that for now, as there is more to look at. But I’ll return to it -W]

Thanks William. Looking forward to your response, and let me note that I appreciate that you won’t jump to judgement on the CMIP3/5 model projections right away. When you look at evidence, please also note that PIOMAS volume again reduced w.r.t. last year, meaning that this coming winter has more catching up to do.